The present invention generally relates to polymers, and compositions containing the same used in chemically amplified resists.
With the increased integration of semiconductor chips, it may be desirable to fabricate a resist capable of forming chips with finer patterns. Thus, it may be necessary to use deep-ultraviolet rays (248 nm) with a shorter wavelength than conventional g-line (436 nm) and i-line (365 nm) rays in order to form resists with these finer patterns.
Conventional chemically amplified resists typically comprise base resins having tert-butoxy carbonyl (t-BOC) pendant groups. In these resins, acidolysis usually occurs readily via an acid catalyst. However, the resins may be undesirable since they often have lower decomposition temperatures as compared to their glass transition temperatures. Thus, a potentially undesirable T-top profile of a pattern may develop in lithography. Accordingly, the resin may become increasingly sensitive to environmental contamination.
In view of the above, it is an object of the present invention to provide polymers which are effectively acidolyzed in the presence of an acid catalyst to potentially exhibit an increased change in polarity.
It is another object of the present invention to provide resist compositions which allow for the formation of high resolution patterns believed to be attributable to a difference in solubility before and after exposure.
It is another object of the invention to provide resist compositions having potentially excellent thermal properties.
These and other objects and advantages are provided by the present invention. In one aspect, the invention relates to polymers used in chemically amplified resists. The polymers are represented by the formula (I): 
wherein R1, R3 and R5 are each independently selected from the group consisting of xe2x80x94H, and xe2x80x94CH3; R2 is selected from the group consisting of t-butyl, tetrahydropyranyl, and 1-alkoxyethyl; R4 is selected from the group consisting of xe2x80x94H, xe2x80x94CH3, t-butyl, tetrahydropyranyl, and 1-alkoxyethyl; x is an integer of 1 to 4, l/(l+m+n) ranges from 0.1 to 0.5, m/(l+m+n) ranges from 0.01 to 0.5, and (l+m)/(l+m+n) ranges from 0.1 to 0.7.
In another aspect, the invention relates to resist compositions. The resist compositions comprise the polymers described by formula (I) and photoacid generators.
The polymers and the resist compositions of the invention are potentially highly advantageous. In particular, because of a potentially large difference in solubility of the resist compositions to developing solutions between before and after exposure, the contrast of the resists is typically excellent. Additionally, due to potentially high decomposition temperatures, the thermal properties of the resist may be highly desirable.
The invention will now be described in greater detail with reference to the preferred embodiments and examples set forth herein. It should be emphasized that these embodiments are only intended to illustrate the invention, and do not limit the scope of the invention as defined by the claims.
In one aspect, the invention relates to polymers represented by the formula (I): 
wherein R1, R3 and R5 are each independently selected from the group consisting of xe2x80x94H, and xe2x80x94CH3; R2 is selected from the group consisting of t-butyl, tetrahydropyranyl, and 1-alkoxyethyl; R4 is selected from the group consisting of xe2x80x94H, xe2x80x94CH3, t-butyl, tetrahydropyranyl, and 1-alkoxyethyl; x is an integer ranging from 1 to 4, l/(l+m+n) ranges from 0.1 to 0.5, m/(l+m+n) ranges from 0.01 to 0.5, and (l+m)/(l+m+n) ranges from 0.1 to 0.7.
In one embodiment, the polymer has a weight-average molecular weight of about 5,000 to about 100,000.
In another embodiment, R1, R3 and R5 are each xe2x80x94H; R2 is t-butyl; and R4 is xe2x80x94H.
In another embodiment, R1, R3 and R5 are each xe2x80x94H; and R2 and R4 are each t-butyl.
In another embodiment, R1, R3 and R5 are each xe2x80x94H; and R2 and R4 are each 1-ethoxyethyl.
In another aspect, the invention relates to resist compositions. The resist compositions comprise the polymers described by formula (I) and photoacid generators.
The photoacid generators may be used in various amounts. Preferably, the resist compositions comprise from about 1 to about 15 percent by weight of the photoacid generators based on the weight of the polymers.
Various materials may be used as photoacid generators, the selection of which are known by those who are skilled in the art. Preferably, the photoacid generators are selected from the group consisting of triarylsulfonium salts, diaryliodonium salts, sulfonates, and mixtures thereof. More preferably, the photoacid generators are selected from the group consisting of triphenylsulfonium triflate, N-hydroxy succine imide triflate, and mixtures thereof.
In one embodiment, the resist compositions may comprise organic bases. The selection of the organic bases are known to one skilled in the art. Preferably, the organic bases are selected from the group consisting of triethyl amine, triisobutyl amine, diethanol amine, triethanol amine and mixtures thereof.
If employed, the organic bases may be used in various amounts. Preferably, the resist compositions comprise from about 0.01 to about 2.0 percent by weight of the organic bases on the basis of the weight of the polymers.
The following examples are provided to illustrate the invention, and are not intended to limit the invention as defined by the claims.